1. Field of the Invention
This invention concerns polyurethane foams, compositions to prepare same, and a process for the preparation of same. Specifically, the invention relates to improved polyurethane foams, having a tough skin, varying in nature from soft to hard, prepared by reacting approximately equal volumes of a mixture of a substantially liquid mixture of an isocyanate and an epoxide supplied from one part of a two part dispensing system with a substantially liquid mixture of a polyether polyol, a catalyst and an accelerator supplied from a second part of a two part dispensing system. The invention also relates to using certain, selected epoxides to impart stability to the mixture of the isocyanate and the epoxide.
2. Description of the Prior Art
Heretofore, it has not been known to prepare polyurethane foams with certain properties from one mixture of an isocyanate and an epoxide and a second mixture of polyether polyol, catalyst and accelerator.
It is known in the art to prepare polyurethanes from a polyol, an isocyanate, a catalyst and an accelerator. It is also known to use epoxides together with polyols, isocyanates, acatalyst and an accelerator to yield polyurethane foams. For example, the patent to Milovanovic-Lerik et al., U.S. Pat. No. 4,789,690, teaches a polyurethane made by first reacting an epoxy resin and an epoxy hardener in the presence of a polyol, and then reacting the resulting polymer polyol dispersion with an isocyanate. The patent to Cuscurida et al., U.S. Pat. No. 4,518,720, discloses a two-step reaction, whereby a polyurethane is formed by adding an epoxy resin-diamine adduct to a polyether polyol, and then reacting such modified polyol with a polyisocyanate. The patent to Brack et al., U.S. Pat. No. 3,184,420, discloses a polyurethane foam made by reacting a polyol containing at least 10% of a linear polymeric ester (prepared by heating either an epoxidized aliphatic acid or a halohydrated saturated aliphatic acid) with a polyisocyanate. The patent to Fontaine et al., U.S. Pat. No. 3,281,379, teaches a process for making a polyurethane foam by reacting a polyol with a polyisocyanate in the presence of a volatile chlorinated lower alkane and an epoxy compound.
Although each of these patents utilizes an epoxide to impart certain characteristics to a polyurethane foam, none of them concerns the specific pre-mixed components described herein having shelf life stability to yield a foam with the improved properties as imparted by the compositions of the instant disclosure. The unique arrangement of components and unique method of reacting the components as disclosed herein yields a polyurethane foam with a tough skin. This improved property is achieved whether the resulting foam is hard or soft.
Further, no known available method to make polyurethanes allows all the reactive components to be packaged in a two part dispensing system, thereby allowing the user to store the components in such a form that can be readily accessed and dispensed at the time when and location where desired for the product polyurethane foam. The foams and methods available in the art described above could not be prepared or accomplished using a two part dispensing system contemplated herein, because (1) the U.S. Pat. No. 4,789,690 and U.S. Pat. No. 4,518,720 each purport to describe the epoxide being first reacted with the polyol and this polyol/epoxide product being then reacted with an isocyanate, and the polyol/epoxide product is believed to be too viscous to be dispensed from the dispensing system contemplated; and (2) the U.S. Pat. No. 3,184,420 and U.S. Pat. No. 3,281,379 each purport to describe a reaction that is accomplished by reacting all the components at once and therefore does not lend itself to use in a two part dispensing system.
By supplying an epoxide and an isocyanate from one part of a two part dispensing system and polyether polyol, catalyst and accelerator from a second part, this invention avoids the viscosity problem that would arise if either the U.S. Pat. No. 4,789,690 or U.S. Pat. No. 4,518,720 method were used, it is believed. The solution to the viscosity problem, however, gives rise to a new problem: once epoxides and isocyanates are mixed, they frequently became unstable as a result of residual hydroxyls present in epoxides that react with the isocyanate, causing premature gelation and shelf life instability. By using selected epoxides, however, this composition disclosed herein solves the problem of shelf life instability.
Accordingly, it is one object of the present invention to provide compositions for the preparation of polyurethane foams, which compositions are nonviscous, are easily dispensed from a two part dispensing system, and have a long shelf life.
It is yet another object of the present invention to provide a method for the preparation of polyurethane foams whereby the components have a long shelf life and can be stored in a two part dispensing system until ready for use.
It is still another object to impart shelf life stability to an isocyanate and epoxide mixture.
It is yet a further object of this invention to provide an improved polyurethane foam with a tough skin.
As described herein, as one skilled in the art would recognize, these and other objects may be accomplished by utilizing the compositions, methods and products more fully described herein.